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--- linux [2025/12/07 12:25] – reddy
+++ linux [2026/03/01 20:25] (current) – reddy
@@ Line 1: / Line 1: @@
-# Linux
+====== Linux ======
-Topics
+===== Popular Topics =====
-  * [[SystemD Unit Files]]
+  * [[bash]]
-  * [[tuned]]
+  * [[bind]]
   * [[Docker]]
+  * [[diff]]
   * [[Git]]
-  * [[VNC]]
+  * [[rsync]]
   * [[Samba]]
+  * [[SystemD Unit Files]]
+  * [[tuned]]
+  * [[Vim]]
+  * [[VNC]]
+===== Miscellaneous =====
+==== Suppressing the Service Restart prompt for "apt install" ====
+<code>
+/etc/needrestart/needrestart.conf
+$nrconf{verbosity} = 0;
+$nrconf{restart} = 'a';
+export DEBIAN_FRONTEND=noninteractive
+export APT_LISTCHANGES_FRONTEND=none
+export NEEDRESTART_MODE=a  # default is "i"nteractive; change to "a"utomatic ; see: /etc/needrestart/needrestart.conf
+export NEEDRESTART_SUSPEND=1
+# echo 'libc6 libraries/restart-without-asking boolean true' | debconf-set-selections
+sudo apt-get remove apt-listchanges --assume-yes --force-yes
+sudo apt-get --force-yes -o Dpkg::Options::="--force-confold" -o Dpkg::Options::="--force-confdef" -fuyq install package-name-here
+</code>
+==== Upgrade to Ubuntu 24.04 LTS ====
+<code>
+sudo apt install -y ubuntu-release-upgrader-core
+# Ensure "Prompt=lts" in "/etc/update-manager/release-upgrades" (instead of "Prompt=normal")
+do-release-upgrade  # Pass "-d" to upgrade before officially supported
+# apt dist-upgrade
+</code>
+==== Limiting Resources ====
+<code>
+mkdir /sys/fs/cgroup/myapp
+CPU_QUOTA=50
+CPU_PERIOD=100
+echo "$CPU_QUOTA $CPU_PERIOD" > /sys/fs/cgroup/myapp/cpu.max
+RAM_QUOTA="1024M"
+echo "$RAM_QUOTA" > /sys/fs/cgroup/myapp/memory.max
+cp /var/run/myappdb/myappd.pid /sys/fs/cgroup/myapp/cgroup.procs
+#rm -Rf /sys/fs/cgroup/myapp
+With tools:
+apt install -y cgroup-tools
+cgcreate -g cpu,memory:/myapp
+cgset -r cpy.max="50 100" myapp
+cgset -r memory.max="1024M" myapp
+cgclassify -g cpu,memory:myapp $(cat /var/run/myappdb/myappd.pid)
+cgexec -g cpu,memory:myapp /usr/bin/myappd --dbpath .
+#cgdelete -g cpu,memory:myapp
+systemd-run -u myappd -p CPUQuota=50% -p MemoryMax=1024M /usr/bin/myappd
+systemd-cgls --all
+systemd-cgtop
+/etc/systemd/system/myapp.slice
+[Slice]
+CPUQuota=50%
+MemoryMax=1024M
+systemctl edit --full myappd.service
+Slice=myapp.slice  #Add to the [Service] section
+systemd-run -u myappd --slice=myapp.slice /usr/bin/myappd
+# To run with Docker
+docker run -d --name db --cgroup-parent=myapp.slice myappimg
+</code>
+==== ssh-copy-id ====
+<code>
+ssh-keygen -f key_file_name
+# To make it non-interactive (we cannot pass the StrictHostKeychecking so we direct the "yes")
+sshpass -p mypassword ssh-copy-id -i key_file_name.pub myuser@myserver <<< yes
+# ssh-copy-id doesn't directly support auth with another key
+# ...but it passes along options to ssh
+ssh-copy-id -i ~/.ssh/id_rsa.nondefault -o 'IdentityFile ~/vm-key' user@remote
+# This can also be done with ssh-agent
+eval $(ssh-agent -s)  # Start the agent
+ssh-add ~/vm-key      # Add the key to the agent
+ssh-copy-id -i ~/.ssh/id_rsa.nondefault user@remote
+eval $(ssh-agent -k)  # Stop the agent
+</code>